The number of patients with metabolic syndrome has currently increased, and is described to reach 20 million including the number of those having a risk of developing the metabolic syndrome in Japan. The metabolic syndrome in severe cases causes arterial sclerosis, resulting in myocardial infarction or cerebral infarction, and thus its early detection and prevention are important. A specific medical checkup (checkup for metabolic syndrome) was made obligatory for the purpose of its early detection in April, 2008. Preventive measures for the metabolic syndrome may include food intake, and functional foods including foods for specified health use have been marketed for preventing obesity and/or the metabolic syndrome.
On the other hand, various marker substances that are included in living bodies and are indicators for diagnosis of diseases have been reported. For example, it has been described in Non-patent Literature 1 that a level of a P-B peptide that is a proline-rich peptide in saliva is significantly reduced in patients with pediatric type I diabetes. It has been also described in Non-patent Literature 2 that polymorphism of a GIPR gene is correlated to a blood glucose level 2 hours after a glucose tolerance test.